CN106415406B

CN106415406B - Image forming apparatus with a toner supply device

Info

Publication number: CN106415406B
Application number: CN201580026961.2A
Authority: CN
Inventors: 松本淳志; 高桥京佑
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2014-05-23
Filing date: 2015-05-22
Publication date: 2020-06-09
Anticipated expiration: 2035-05-22
Also published as: GB2541622A; DE112015002439T5; GB201621696D0; WO2015178506A1; US20170068183A1; GB2541622B; CN106415406A; US9946191B2; JP2015222394A; JP6366363B2

Abstract

The present invention properly performs developer discharge in a configuration in which the feeding force of a first feed screw (25) against a developer in a region opposed to a discharge port (40) for discharging the developer is low. The first feed screw (25) has its blades cut off in a first region including a portion opposite to the discharge port (40). Thereby, the developer feeding force in the first region is lower than the developer feeding force in the second region adjacent to the first region. A humidity detection unit as an acquisition unit detects developer humidity as information on a charge amount of the developer. A CPU as a control unit controls, based on the developer humidity (H) detected by the humidity detection unit, the driving speed at which the feed screws (25, 26) are driven to be faster in a case where the developer humidity is a second humidity higher than a first humidity than in a case where the developer humidity is the first humidity.

Description

Image forming apparatus with a toner supply device

Technical Field

The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, a multifunction machine having a plurality of functions of these machines, and the like.

Background

Generally, in an electrophotographic image forming apparatus, an electrostatic latent image formed on a photosensitive drum as an image bearing member is developed as a toner image by a developing device as a developing means using a developer containing toner and carrier (carrier). In such a developing apparatus, in a circulating path in a developing container, toner and carrier are triboelectrically charged by feeding the developer while agitating the developer by rotating a feeding screw. The developer containing the toner and the carrier gradually reduces the charging performance of the carrier by continuous circulation of the carrier which is subjected to friction in the developing container without being consumed by image formation. For this reason, it is conventional to secure the average charging performance of the carrier in the developer by discharging a part of the developer in such a manner as to overflow from a discharge port provided in the developing container while supplying new (fresh) developer to the developing container (japanese patent publication No. 2-21591).

Further, there is proposed a developing apparatus configured such that a force with respect to a circumferential direction or an outward radial direction, which acts on a developer by rotation of a feed screw in a region opposed to a developer discharge port, is smaller than that in other regions (japanese patent laid-open No. 2000-112238). Specifically, a configuration is adopted in which the blade of the feed screw in the region opposite to the developer discharge port is small, or a configuration in which the blade is omitted (removed).

Disclosure of Invention

[ problem to be solved by the invention ]

Here, as in the configuration described in japanese patent laid-open No. 2000-112238, when the blade of the feed screw in the region opposite to the discharge port is removed or made small in diameter, the developer feeding force of the feed screw in the region is lowered. Then, in the vicinity of the discharge port, the developer fed by the feed screw stagnates and the developer surface rises, so that the developer passing over the discharge port is discharged so as to be flush and overflow the discharge port.

However, in the configuration in which the developer is thus retained, when the charge amount of the developer is reduced, the fluidity of the developer becomes high, and therefore the degree of retention of the developer in the vicinity of the discharge port becomes small, so that the developer is not easily discharged through the discharge port. As a result, the amount of developer in the developing container increases, so that in some cases, the developer overflows the discharge port during the ascent or the like of the developing device, and the rotational load of the feed screw becomes high and the possibility of the feed screw locking increases.

In view of the above circumstances, the present invention has been achieved to appropriately discharge developer in a configuration in which the developer feeding force of the feed screw in the region opposed to the discharge port is low.

[ means for solving problems ]

According to an aspect of the present invention, there is provided an image forming apparatus including: an image bearing member; a developing device configured to develop a latent image formed on the image bearing member, and including a developing container containing a developer, a feed screw configured to feed the developer in the developing container, and a discharge port provided at a side of the developing container to be opposed to the feed screw and configured to allow discharge of an excessive amount of the developer in the developing device; a supply device configured to supply a developer into the developing container; a drive device configured to rotationally drive the feed screw; an acquisition section configured to acquire information on a charge amount of the developer; and a controller configured to control the driving device, wherein the feed screw is formed such that an outer diameter of a first region including a portion opposing the discharge port is smaller than an outer diameter of a second region adjacent to the first region, and wherein the controller performs control such that a driving speed at which the feed screw is driven by the driving device is faster in a case where a charge amount of the developer corresponds to a second charge amount lower than a first charge amount than in a case where the charge amount of the developer corresponds to the first charge amount, based on the information of the acquisition section.

According to the present embodiment, in a state where the fluidity of the developer becomes high and the charge amount is low, control is performed so that the feed screw driving speed becomes fast (high), and therefore, even when the fluidity of the developer is high and the developer is not easily stagnated in the vicinity of the discharge port, the developer surface is raised and the discharge of the developer can be appropriately performed.

Drawings

Fig. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention.

Fig. 2 is a schematic cross-sectional structural view of a developing apparatus according to the first embodiment.

Fig. 3 is a schematic longitudinal structural view of the developing apparatus.

Fig. 4 is a schematic view showing a feed screw in the vicinity of the developing apparatus according to the first embodiment.

Fig. 5 includes schematic views showing other 3 examples of the feed screw near the developing device according to the first embodiment.

Fig. 6 is a diagram illustrating the discharge characteristics of the developer through the discharge port.

Fig. 7 is a schematic view showing the developer surface in the vicinity of the discharge port.

In fig. 8, (a) is a schematic view showing a developer surface in the vicinity of the discharge port in the case where the fluidity of the developer is low, and (b) is a schematic view showing a developer surface in the vicinity of the discharge port in the case where the fluidity of the developer is high.

Fig. 9 is a control block diagram of the image forming apparatus according to the first embodiment.

Fig. 10 is a flowchart of control during the ascent of the developing device in the first embodiment.

Fig. 11 is a graph showing a change in the developer amount in the developing container with respect to the developer humidity at each image duty in the comparative example of the present invention.

Fig. 12 is a graph showing a change in the developer amount in the developing container with respect to the developer humidity at each image duty in embodiment 1 of the present invention.

Fig. 13 is a control block diagram of an image forming apparatus according to a second embodiment of the present invention.

Fig. 14 is a flowchart of control during the ascent of the developing device in the second embodiment.

Fig. 15 is a graph showing a change in the developer amount in the developing container with respect to the developer humidity at each image duty in embodiment 2 of the present invention.

Fig. 16 is a control block diagram of an image forming apparatus according to a third embodiment of the present invention.

Fig. 17 is a flowchart of control during the ascent of the developing device in the third embodiment.

Fig. 18 is a graph showing a change in the developer amount in the developing container with respect to the developer humidity at each image duty in embodiment 3 of the present invention.

Fig. 19 is a flowchart of control during the ascent of the developing device in the fourth embodiment of the present invention.

Fig. 20 is a flowchart showing another flow in the case where K is 1 in the flow of fig. 19.

Fig. 21 is a schematic cross-sectional structural view of a developing apparatus in the first example in other embodiments of the present invention.

Fig. 22 is a schematic cross-sectional structural view of a developing apparatus in a second example in other embodiments of the present invention.

Detailed Description

< first embodiment >

A first embodiment of the present invention will be described with reference to fig. 1 to 12. First, the overall structure of the image forming apparatus in the present embodiment will be described with reference to fig. 1.

[ image Forming apparatus ]

The image forming apparatus 100 in the present embodiment is a full-color image forming apparatus employing an electrophotographic type, and includes four image forming portions P (Pa, Pb, Pc, Pd). Each of the image forming portions Pa to Pd includes a drum-shaped electrophotographic photosensitive member, i.e., photosensitive drum 1(1a, 1b, 1c, 1d). Around the photosensitive drum 1, there are disposed charging devices 2(2a, 2b, 2c, 2d), developing devices 4(4a, 4b, 4c, 4d), primary transfer rollers 6(6a, 6b, 6c, 6d), cleaning devices 19(19a, 19b, 19c, 19d), and the like. Further, above the photosensitive drum 1 in fig. 1, a laser beam scanner 3(3a, 3b, 3c, 3d) as an exposure means is placed.

The respective image forming portions Pa, Pb, Pc, Pd have substantially the same configuration except that the colors of the toners are different from each other, and therefore, hereinafter, suffixes (a, b, c, d) of reference numerals showing constituent elements or portions of the relevant image forming portions will be omitted from the description as long as there is no particular need.

Next, an image forming sequence of the entire image forming apparatus having the above-described configuration will be described. First, the photosensitive drum 1 is uniformly charged by the charging device 2 as a charging member. Then, the uniformly charged photosensitive drum 1 is subjected to scanning exposure by the laser beam scanner 3 and exposed to laser light modulated by an image signal. The laser beam scanner 3 incorporates therein a semiconductor laser which is controlled in correspondence with an original image information signal output from an original reader including a photoelectric conversion element such as a CCD, and emits laser light.

As a result, the surface potential of the photosensitive drum 1 charged by the charging device 2 changes at the image portion, so that an electrostatic latent image is formed on the photosensitive drum 1. This electrostatic latent image is reversely developed into a visible image (i.e., a toner image) with toner by a developing device 4 as a developing means. In the present embodiment, the developing device 4 uses a two-component contact development type in which a developer containing a toner and a carrier is mixed to be used as the developer.

Further, the above-described steps are performed for each of the image forming portions Pa, Pb, Pc, Pd, so that four color toner images of yellow, magenta, cyan, black are formed on the

photosensitive drums

1a, 1b, 1c, 1d, respectively. In the present embodiment, an intermediate transfer belt 5 composed of an endless belt as an intermediate transfer member is disposed at a position below the image forming portions Pa, Pb, Pc, Pd. The intermediate transfer belt 5 is stretched by

rollers

61, 62, 63 and is movable in the arrow direction.

The toner images on the photosensitive drums 1 are sequentially transferred at a time onto the intermediate transfer belt 5 by the primary transfer rollers 6. Thereby, four color toner images of yellow, magenta, cyan, and black are superimposed on the intermediate transfer belt 5, thereby forming a full color image. Further, the toner remaining on the photosensitive drum 1 without being transferred to the intermediate transfer belt 5 is recovered by the cleaning device 19.

The full-color image on the intermediate transfer belt 5 is transferred onto a recording material (sheet) S such as paper or a sheet taken out of a cassette 12 and passed through a feeding roller 13 and a guide 11 by the action of a secondary transfer roller 10 as a secondary transfer member. The toner remaining on the surface of the intermediate transfer belt 5 without being transferred to the recording material S is recovered by the intermediate transfer belt cleaning apparatus 18.

On the other hand, the recording material S on which the toner image is transferred is sent to a fixing device 16, and the toner image is fixed on the recording material S by heating and pressing. The recording material S on which the toner image is fixed is discharged onto a discharge tray 17.

Incidentally, in the present embodiment, as the image bearing member, the photosensitive drum 1 of a drum-shaped organic photosensitive member which is generally used is used, but an inorganic photosensitive member, for example, an amorphous silicon photosensitive member may also be used. Further, a belt-shaped photosensitive member may also be used. Further, as for the charging type, the transfer type, the cleaning type, and the fixing type, they are also not limited to those described above.

[ developing apparatus ]

Next, the developing device 4 in the present embodiment will be described more specifically using fig. 2 and 3. The developing device 4 includes a developing container 22, and accommodates a two-component developer containing toner and carrier as a developer in the developing container 22. Further, in the developing container 22, a developing sleeve 28 as a developer carrying member and a developing blade (leveling blade) for regulating a developer chain carried on the developing sleeve 28 are disposed. The interior of the developing container 22 is vertically divided into the developing chamber 23 and the stirring chamber 24 by a partition wall 27, and contains the developer, wherein a substantially central portion of the partition wall 27 extends in a direction perpendicular to the paper surface of the figure, and the developer is contained in the developing chamber 23 and the stirring chamber 24.

In the developing chamber 23 and the stirring chamber 24, a first feeding screw 25 and a second feeding screw 26 are respectively provided as developer feeding members. The first feed screw 25 is disposed at the bottom (part) of the developing chamber 23, substantially parallel to the axial direction of the developing sleeve 24. Further, the first feed screw 25 rotates in an arrow direction (clockwise direction) shown in the figure, supplies the developer in the developing chamber 23 to the developing sleeve, and feeds the developer in one direction along the axial direction.

Further, a second feed screw 26 is disposed at the bottom (part) of the stirring chamber 24, substantially parallel to the first feed screw 25. Further, the second feed screw 26 rotates in the direction (counterclockwise) opposite to the rotational direction of the first feed screw 25, recovers the developer after development, and feeds the developer in the agitation chamber 24 in the direction opposite to the first feed screw 25. Therefore, the developer is fed by the rotations of the first and second feed screws 25 and 26, and circulated between the developing chamber 23 and the agitating member 24 through the openings 11 and 12 (i.e., communicating portions) formed at both ends of the partition wall 27.

Next, a driving system of the developing device 4 will be described using fig. 2. The developing sleeve 28 is rotationally driven by a first drive motor M1, and the first feed screw 25 and the second feed screw 26 are rotationally driven by a second drive motor M2 as a driving member. In the present embodiment, both motors use a DC motor, and the driving rotational speed in a steady state during image formation is 300(rpm) for the first drive motor M1 (with respect to the second drive motor M2, which will be described later). The first drive motor M1 is directly connected to the developing sleeve 28, and the second drive motor M2 is directly connected to the first feed screw 25. Further, the first feed screw 25 and the second feed screw 26 are driven at a ratio of 1:1.07 by gears.

In the present embodiment, the developing container 22 is provided with an opening at a position corresponding to a developing region where the developing container 22 opposes the photosensitive drum 1. Here, the rotation speed of the developing sleeve 28 was set to 300rpm, and the diameter was set to 20 mm. The rotation speed of the photosensitive drum 1 was set to 120rpm, and the diameter was set to 30 mm. Further, the distance in the closest region between the developing sleeve 28 and the photosensitive drum 1 is about 400 μm, so that setting is made such that development can be performed in a state where the developer fed to the developing portion is in contact with the photosensitive drum 1.

The developing sleeve 28 is formed of a non-magnetic material such as aluminum and stainless steel, and inside thereof, a magnet roller 28m as a magnetic field (generating) member is disposed in a non-rotating state. This developing sleeve 28 rotates in the direction indicated by the arrow in the figure (counterclockwise direction), and feeds the layer thickness regulated two-component developer to the developing region where the developing sleeve 28 opposes the photosensitive drum 1 by cutting the magnetic brush chain with the regulating blade 29. Then, the developing sleeve 28 supplies the developer to the electrostatic latent image formed on the photosensitive drum 1, and develops the electrostatic latent image with toner.

The regulation blade 29 as the above-described chain cutting member is constituted by a nonmagnetic member 29a and a magnetic member 29b such as an iron material, and the nonmagnetic member 29a is formed of an aluminum plate or the like extending in the longitudinal axial direction of the developing sleeve 28. Further, by adjusting the gap between the regulating blade 29 and the developing sleeve 28, the amount of the developer supplied to the developing region is regulated. In the present embodiment, the coating amount per unit area of the developer on the developing sleeve 28 is adjusted to 30mg/cm by the regulating blade 29². Incidentally, the gap between the regulating blade 29 and the developing sleeve 28 is set to 200-. In the present embodiment, the gap is set to 400 μm.

[ developer ]

Next, a two-component developer containing a toner and a carrier used in the present embodiment will be described. The toner mainly contains a binder resin and a colorant, and colored resin particles (including other additives) and colored particles having an external additive (for example, fine particles of choroidal silica) are added to the outside of the toner as needed. The toner is a negatively chargeable polyester resin, and desirably has a volume average particle diameter of not less than 4 μm and not more than 10 μm, preferably not more than 8 μm. Further, as the carrier, metal particles whose surfaces have been oxidized or not oxidized, for example, iron, nickel, cobalt, manganese, chromium, rare earth metals, alloys of these metals, and oxide ferrite, can be preferably used. The method for producing these magnetic particles is not particularly limited. The weight average particle diameter of the carrier may be 20 to 60 μm, preferably 30 to 50 μm, and the specific resistance of the carrier may be not less than 10⁷Ohm-cm, preferably not less than 10⁸Ohm cm. In this example, a resistivity of 10 is used⁸Ohm cm support.

[ supply of developer ]

Next, a developer supply method in the present embodiment will be described using fig. 2 and 3. Above the developing device 4, a hopper 31 containing a two-component developer containing a toner and carrier mixture for supply is provided. The hopper 31 constituting the supply means includes a supply screw 32 as a spiral-shaped supply member at a lower portion thereof, and one end of the supply screw 32 extends to a position of the developer supply port 30 provided at a front end portion of the developing device 4. By the rotational force of the supply screw 32 and the gravity of the developer, an amount of toner corresponding to the amount of toner consumed by image formation is supplied from the hopper 31 to the developing container 22 through the developer supply port 30. Thus, the supply developer is supplied from the hopper 31 to the developing device 4. The supply amount of the supplied developer is roughly determined by the number of revolutions of the supply screw 32 as a feeding member, but the number of revolutions is determined by a toner supply amount control means, not shown. As the toner supply amount control method, a method of optically or magnetically detecting the toner content (density) of a two-component developer, a method of detecting the density of a toner image obtained by developing a reference latent image on the photosensitive drum 1, and the like are known, and therefore, any of these methods can be appropriately selected.

[ discharge of developer ]

Next, a developer discharging method in the present embodiment will be described using fig. 3. In the present embodiment, the developing container 22 is provided at a predetermined height position thereof with a discharge port 40 for allowing discharge of the developer. Specifically, the discharge port 40 is disposed outside the developing sleeve placement region on the downstream side of the developing chamber 23 with respect to the developer feeding direction, and the developer is discharged through the discharge port 40. When the amount of the developer in the developing device 4 increases in the developer supplying step as described above, the developer is discharged through the discharge port 40 in an overflow manner according to the amount of increase. Incidentally, the position of the discharge port 40 with respect to the developer supply direction is on the upstream side of the position of the developer supply port 30 with respect to the developer supply direction. This is because the supplied fresh (new) developer is prevented from being immediately discharged. Further, in consideration of developer discharge characteristics described later, the height position of the discharge port 40 is set so that the amount of developer in the developing container 22 is an appropriate amount.

Further, in the case of the present embodiment, as shown in fig. 4, the first feed screw 25 in the developing chamber 23 is formed by cutting away a part of the blade 25b formed spirally around the rotary shaft 25a, that is, in the first region α including the portion opposed to the discharge port 40 in the first feed screw 25a, only the rotary shaft 25a is present and the blade 25b is not present, on the other hand, in the second region β adjacent to the first region α, the blade 25b is present, whereby the developer feeding force of the first feed screw 25a in the first region α is made smaller than that of the first feed screw 25a in the second region β, further, in the present embodiment, in the first region α, only the rotary shaft 25a is present and the blade 25b is present in the second region β, and therefore, the outer diameter of the first feed screw 25 in the first region α (the outer diameter of the rotary shaft 25 a) is smaller than the outer diameter of the blade 25b (the outer diameter of the first feed screw 25b in the second region).

In the case of the present embodiment, by adopting such a configuration, the developer is not easily fed into the first region α, and therefore, the developer stagnates in the vicinity of the discharge port 40, and the developer face rises, so that the developer is discharged through the discharge port 40, in the present embodiment, the first region α portion where the blade 25b of the first feeding screw 25 is cut out is 14mm in length, and the length of the discharge port 40 in the screw axial direction is 10mm, the center of the first region α portion with respect to the screw axial direction and the center of the discharge port 40 with respect to the screw axial direction are arranged to coincide with each other.

Here, in the present embodiment, by cutting off a part of the blade of the screw, the developer feeding force in the first area is made smaller than the developer feeding force in the second area. However, in addition to cutting out the blades as described above, the change in the feeding force may be performed by appropriately adjusting the outer diameter, pitch, angle, and the like of the blades. For example, the feed screw may also be formed such that the outer diameter of the blades formed helically about its axis of rotation may also be smaller in the first region than in the second region.

Alternatively, as shown in fig. 5, a

member

41a, 41b, or 41c having an outer diameter smaller than that of the blade formed in the second region may be provided in the first region. The member 41 in fig. 5 (a) is a rectangular rib extending radially from the rotation shaft 25a. The member 41b in fig. 5 (b) is a rib whose rib cross section is gradually narrowed from the base toward the free end of the rotating shaft 25a. The ribs in (a) and (b) of fig. 5 have a cross-sectional shape perpendicular to the rotation shaft 25a so as to have the same phase and the same shape along the rotation shaft 25a. For this reason, each rib agitates the developer with respect to the rotational direction of the rotary shaft 25a, and the (developer) feeding force toward the rotary shaft 25a is substantially zero. The member 41c in fig. 5 (c) is a rib, each rib having a rectangular shape and disposed at an angle with respect to the rotation shaft 25a. By providing these

members

41a, 41b, and 51c, it is possible to further stably discharge the developer by leveling and averaging the developer surface while retaining the developer in the portion opposing the discharge port 40. However, in the case of either structure, the screw outer diameter in the first region is made smaller than the screw outer diameter in the second region. This is because when the screw outer diameter becomes large, the developer is easily discharged through the discharge port 40 by jumping of the developer.

Fig. 6 shows a graph of the developer discharge characteristic in the present embodiment. When the amount of the developer in the developing container 22 is a variable, the developer discharge characteristic is a developer discharge amount per unit time. The amount of the developer in the developing container 22 is determined by achieving a balance between the discharge amount per unit time and the difference between the supply amount per unit time of the developer supplied to the developing container 22 and the amount of the toner subjected to development (of the latent image). That is, the developer amount in the developing container 22 can be approximately expressed as a value between the developer amount shown by the intersection a between the minimum supply amount per unit time and the discharge characteristic line, and the developer amount shown by the intersection b between the maximum supply amount per unit time and the discharge characteristic line. In other words, these intersection points are points at which the developer amounts balance each other during the minimum feeding period and the maximum feeding period. When the amount of the developer in the developing container 22 becomes significantly small, the developer carrying amount of the developing sleeve 28 is insufficient (improper coating is generated), so that density unevenness is liable to be generated. On the other hand, the amount of developer in the developing container 22 becomes significantly large, and when the developing device 4 is changed from the drive off state to the drive on state, there is a possibility that the developer is caused to overflow during the ascent.

In general, the developer discharge characteristic can be measured in the following manner. In a state where the developing sleeve 28 and the first and second feed screws 25 and 26 are driven at a desired peripheral speed, the developer is placed in the developing container 22 until the developer is uniformly coated on the developing sleeve 28. The developing sleeve 28 and the first and second feed screws 25, 26 are driven at a desired peripheral speed until the developer circulation in the developing container 22 is in a steady (steady) state (typically 1 or 2 minutes). From the time when the coating on the developing sleeve 28 becomes uniform, the developer is gradually added into the developing container 22 through the developer supply port 30. In the present embodiment, 10g of the developer was added, and the discharge amount was measured within 30 seconds, thereby measuring the developer discharge amount per unit time.

The above is the discharge characteristic at a certain drive speed of both the developing sleeve 28 and the first feed screw 25, and in the case where there are a plurality of drive speeds, the above-described minimum developer amount a must be uniformized to the extent possible at these drive speed(s). If this is not the case, the possibility of problems such as improper developer coating or the like occurring during speed switching increases.

Here, as described above, by removing the blade 25b in the first region α including the portion opposed to the discharge port 40 of the first feed screw 25, in the first region α, the developer feeding performance is lower than that in the second region β located on the upstream side of the first region α with respect to the developer feeding direction, then, as shown in fig. 7, the developer stagnates in the region where the developer feeding performance is lowered, whereby the developer surface is raised, and therefore, it is intended to achieve developer surface-dependent (developer) discharge while suppressing jumping of the developer.

However, the degree of retention (the degree of elevation of the developer surface) in this region opposite the discharge port 40 significantly depends on the fluidity of the developer. In fig. 8, (a) shows developer surface behavior in a region opposing the discharge port 40 in the case where the developer charging amount is high and the developer fluidity is low, and (b) shows developer surface behavior in the case where the developer charging amount is low and the developer fluidity is high. In the figure, solid arrows indicate the developer feeding speed at the relevant points. That is, when the length of the solid arrow is long, the arrow indicates that the feeding speed is fast. Further, the broken-line arrow indicates the degree of elevation of the developer surface in the region opposed to the discharge port 40, and when the length of the arrow is long, the arrow indicates that the degree of elevation is large.

As can be seen from (a) of fig. 8, in the case where the developer is high in electrification amount and low in developer fluidity, the difference between the feeding speed of the developer in the region opposed to the discharge port 40 and the feeding speed on the upstream side thereof is large, so that the speed of the developer is greatly reduced and stagnates in the region opposed to the discharge port 40. This causes the developer surface to rise, thereby facilitating the discharge of the developer. On the other hand, as can be seen from (b) of fig. 8, in the case where the developer amount is low and the developer fluidity is high, the above speed difference is small, and even when the developer feeding force is reduced in the region opposed to the discharge port, the speed of the developer is hardly reduced. Therefore, the developer surface does not rise, and the developer discharge is suppressed.

This is because coulomb interaction between developer particles in the developer is small in the case where the developer charge amount is low. As a result, a force for transmitting a force received from the wall surface of the developing container 22 through the surface layer of the developer into the developer becomes small, and a force for deforming the shape of the developer becomes small. This is one of the main reasons. That is, the toner in the developer exists in a state where the toner is attracted to the carrier by electrostatic force by being charged. The polarity between toners and the polarity between charge amounts are the same, and the toners and the carriers have different polarities. The carrier is attached to another carrier via the toner while being subjected to a repulsive force of the other carrier, and similarly, the toners are also repelled from each other while the toners are attracted to each other by the carrier. Therefore, with a large electrostatic force as an attraction force, the developer deviates from movement according to gravity (i.e., fluidity is high). In other words, the developer is disturbed by the electrostatic force, and the fluidity is reduced. On the other hand, with a smaller electrostatic force, i.e., with a lower developer charge amount, the movement according to gravity is not disturbed, and the fluidity becomes high. In addition, this is because the force itself received by the surface layer of the developer from the wall surface of the developing container 22 is small.

Therefore, when the charge amount is low and the developer discharge is suppressed, the developer amount is continuously increased until the developer discharge amount and the developer supply amount balance each other, so that the difference between the balanced developer amount and the limit developer amount at which the developer overflows becomes small. Further, robustness against developer overflow becomes small, and the risk of developer overflow due to developer surface fluctuation (e.g., electric charge) of the moment from the drive off to the drive on (during ascent or the like) of the developing device 4 becomes large.

As an effective means for solving such a problem, it is conceivable to increase the screw rotation speed. This is because when the screw rotation speed increases, even in the case where the amount of electrification is small and the fluidity is high, the developer loses the feeding force at the stagnating portion opposite to the discharge port, and the developer from the rear hits the developer, slightly decreasing the speed, and therefore the developer surface rises due to its kinetic energy. However, in the case where the developer charge amount in which it is not necessary to initially increase the screw rotation speed is high, when the screw rotation speed is increased, a high load is applied to the developer having low fluidity. For this reason, screw locking and developer deterioration due to an increase in the load of the screw progress significantly. Therefore, it is not preferable that the screw rotation speed is always increased.

[ control of screw rotation speed ]

Therefore, in the present embodiment, information on the developer charging amount is acquired, and based on the information, the driving speed (screw rotation speed) of the first feeding screw 25 is controlled. That is, based on the information of the acquisition section, the driving speed at which the first feed screw 25 is driven by the second drive motor M2 is made faster in the case where the developer charging amount corresponds to the second charging amount lower than the first charging amount than in the case where the developer charging amount corresponds to the first charging amount. In the present embodiment, as information on the charge amount of the developer, the developer humidity is detected. For this purpose, as shown in fig. 9, the image forming apparatus in the present embodiment includes a CPU 50 as a control means, a memory 51 as a storage means, a counter 52 for counting the number of image-formed sheets (the number of sheets subjected to image formation), and a humidity detection section 53 as an acquisition section and a humidity detection section. Each of the first drive motor M1 for driving the developing sleeve 28 and the second drive motor M2 for driving the first feed screw 25 is controlled by the CPU 50.

Here, the reason why the humidity is a parameter is that the developer charging amount depends on the developer humidity. That is, there is a tendency that: the developer charge amount becomes lower as the developer humidity becomes higher, and the developer charge amount becomes higher as the developer humidity becomes lower. Further, in the present embodiment, the driving speed of the first feed screw 25 is controlled while substantially maintaining the rotational speed ratio between the first feed screw 25 and the second feed screw 26 in relation to the circulation of the developer. That is, even in the case where the rotational speed of the first feed screw 25 opposite to the discharge port 40 is changed, the developer conveyance efficiency between the

screws

25, 26, etc. is not changed, and only the discharge characteristics in the vicinity of the discharge port 40 are controlled. Thereby, the developer discharge can be improved without greatly interfering with the entire developer circulation. However, although the rotation speed ratio between the screws associated with the developer circulation does not strictly coincide, when the difference in rotation speed ratio is around ± 1% of the screw rotation speed, the difference may be considered to be substantially constant, and therefore, the rotation speed ratio may also be changed. In the present embodiment, the first feed screw 25 and the second feed screw 26 are connected to each other by gears to maintain the rotation speed ratio.

Further, the humidity detecting portion 53 detects information (humidity information) related to the humidity of the developer. In the present embodiment, the humidity detection portion 53 includes a water content sensor 54 as a water content detection means, a temperature sensor 55 as a temperature detection means, and a calculation portion 56 as a calculation means. The water content sensor 54 detects the water content outside the image forming apparatus. For this reason, the water content sensor 54 is provided outside the apparatus main assembly. The temperature sensor 55 detects the temperature in the developing container. For this reason, the temperature sensor 55 is disposed inside the developing container. The calculation portion 56 calculates the developer humidity from the relationship between the temperature detected by the temperature sensor 55 and the water content detected by the water content sensor 54. For this reason, in the calculation portion 56, a table in which the relationship between the temperature, the water content, and the humidity is set, a calculation formula for acquiring the humidity from the relationship between the temperature and the humidity, and the like are stored, so that the humidity can be calculated from the temperature and the water content. Incidentally, the calculation (calculation) by the calculation section 56 may also be performed by the CPU 50. In addition, the table and the calculation formula may also be stored in the memory 51.

In the present embodiment, information on the humidity detected by the humidity detecting portion 53 is stored in the memory 51. Further, during the ascent of the developing device 4, that is, when the first drive motor M1 and the second drive motor M2 are changed from the drive-off state to the drive-on state by inputting an image forming job or the like, the control of the drive speed of the first feed screw 25 is performed. In the present embodiment, a table as shown in table 1 is stored in the memory 51. Then, during the rising of the developing device 4 (the timing of switching from OFF to ON or immediately before the timing), the CPU 50 reads the humidity information at this time from the memory 51, and determines the driving speed of the first feed screw 25 (screw rotation speed) from the table of table 1 based ON the humidity information. In the present embodiment, as shown in table 1, three tables are provided, and each table can be selected by a user or the like in the service mode. The initial settings are table 2.

Table 1 all units are rpm

In each table of table 1, the screw rotation speed (unit: "rpm") is set for the developer humidity (relative humidity). Incidentally, table 1 is a mode in which the screw rotation speed is constant regardless of the developer humidity. On the other hand, in tables 2 and 3, the screw rotation speed is set so that the rotation speed is faster in the case where the developer humidity is the second humidity (for example, more than 15%) higher than the first humidity than in the case where the developer humidity is the first humidity (for example, 15% or less). That is, the screw rotation speed is made faster in the case where the humidity information detected by the humidity detection portion 53 corresponds to the second humidity higher than the first humidity than in the case where the humidity corresponds to the first humidity.

Incidentally, in the present embodiment, the humidity information for the screw rotation speed is updated by an instruction of the CPU 50 at a predetermined timing. The predetermined timing is during the activation of a main switch of the image forming apparatus, during the start of an image forming job, at the time when a predetermined time elapses, or the like, but in the present embodiment, the information on the humidity is updated when image formation is performed not less than a predetermined number of sheets. For this reason, the number of image forming sheets is counted by the counter 52, and when the value counted by the counter 52 during the ascent of the developing device 4 is not less than the predetermined number of sheets, the humidity information stored in the memory 51 is updated by the CPU 50. Then, the CPU 50 controls the screw rotation speed based on the humidity information.

Using fig. 10, a specific example of control in the present embodiment will be described. In the present embodiment, the flowchart of fig. 10 is executed every time the developing device 4 is raised (OFF/ON), and the driving is started at the screw rotation speed acquired therefrom. That is, in the present embodiment, the timing of change in the screw rotation speed is the timing of development drive OFF/ON.

First, every time the developing driver is OFF/ON, the number of image forming sheets (print number) c (n) at this time is read from the memory 51, and the image forming sheets number c (n) is compared with the print number Ch in which the last screw rotation speed was changed with humidity (S1). Then, when c (n) -Ch is not less than 300 sheets (yes at S1), the developer humidity at this time is read from the memory 51 and set as the developer humidity H for screw rotation speed control (S2). The developer humidity is calculated every printing and stored in the memory 51. Thereafter, the print number c (n) at this time is set to Ch, which is the number of sheets of which the screw rotation speed was changed last (S3), and the development drive is actuated using the developer humidity H stored in the memory 51 (S4). That is, the screw rotation speed at the developer humidity H is read from the table of table 1, and the drive of the developing device is actuated at the screw rotation speed. On the other hand, in S1, when the difference from the print number Ch in which the last screw rotation speed changes with humidity is less than 300 sheets (no of S1), the development drive is actuated using the last developer humidity H (S4). That is, H is not updated, and therefore, the development drive is actuated at the screw rotation speed of the last time as it is.

By performing the above control, the screw rotation speed is varied at a certain frequency (300 sheets or more in the present embodiment), so that the screw rotation speed corresponding to the developer humidity at that time can be set. The above frequency may also be one sheet or more, that is, the screw rotation speed may be changed per printing, but the actual humidity change of the developer with respect to the humidity change in the developing container is slow, and therefore, the frequency does not need to be changed, and in the present embodiment, the frequency is the above-described number of sheets.

Further, in the present embodiment, the control of fig. 10 is performed during the ascent of the developing device 4, but the control may also be performed at another timing, for example, at an image and an interval between images (sheet interval) during execution of an image forming job. However, the control of fig. 10 is accompanied by a change in the screw rotation speed according to a change in humidity, and therefore may preferably be performed during the ascent of the developing device 4. That is, it is relatively difficult to control the variation in the screw rotation speed during driving of the developing device 4, and therefore the variation in speed can be easily performed by actuating the developing device 4 at a varying speed during driving actuation. Further, in the present embodiment, even during execution of the image forming job, OFF/ON of the development drive is forcibly performed once every predetermined number of image forming sheets (for example, 150 to 170 sheets). For this reason, the control of fig. 10 is performed at a certain frequency regardless of the number of image formation sheets of the image forming job.

In the case of the present embodiment as described above, in a state where the charge amount is low where the developer fluidity is high, that is, in a state where the developer humidity is high, control is performed so that the driving speed of the first feed screw 25 is fast. For this reason, even when the developer fluidity is high and the developer is not easily stagnated in the vicinity of the discharge port 40, the developer surface is raised, so that the discharge of the developer can be appropriately performed. That is, as described above, when the screw rotation speed is increased, even in the case where the fluidity is high, the developer loses the feeding force at the stagnating portions opposed to the discharge ports, and the developer from the rear hits the developer, slightly decreasing the speed, and therefore the developer surface is raised due to its kinetic energy. For this reason, the developer can be appropriately discharged through the discharge port 40.

The effects of the present embodiment as described above will be described using fig. 11 and 12. Fig. 11 and 12 show the results of experiments performed to confirm the effects of the present example. For each of comparative examples in which the screw rotation speed was made constant regardless of the developer humidity and example 1 in which the screw rotation speed was varied with the developer humidity as in the present example, an experiment was performed under the following conditions. First, the image duty (image duty) is changed to a plurality of levels, the developing device is driven in each of the environments in which the developer humidity is different, and the developer amounts in the developing containers are compared. Fig. 11 and 12 show developer amounts, fig. 11 shows results of comparative example, and fig. 12 shows results of example 1.

Incidentally, in the comparative example, the screw rotation speed was constantly 700 (rpm). In example 1, the screw rotation speed was controlled using table 2 of table 1. Further, the image duty is represented by a percentage of a ratio of the total amount of toner of the image on the photosensitive drum to the maximum total amount of toner of each image on the photosensitive drum. The maximum total amount is a toner consumption amount when a latent image is developed with toner over the entire surface of an image formable region on a photosensitive drum (during entire region solid development), and an image duty during the entire region solid development is 100%.

According to fig. 11, in the case of the comparative example in which the screw rotation speed is not controlled and made constant according to the humidity, the developer amount greatly fluctuates according to the humidity. In particular, in the case where the humidity of the developer is 60%, the discharged amount of the developer is significantly reduced and compensated with the amount of the developer in the developing container, and thus the amount of the developer is significantly increased as compared to when the humidity is 10%. The broken line in fig. 11, 12 indicates a limit line of the overflow, and when the developer humidity is high, the charge amount is reduced and the volume is reduced, so the overflow limit line moves to a larger side, but the degree of increase of the developer due to improper developer discharge under high humidity is larger than the degree of increase of the developer amount of the overflow limit line.

In summary, in the comparative example, robustness becomes lower for developer overflow with higher humidity, so that the risk of developer overflow due to developer surface fluctuation of moment during driving actuation of the developing device or the like becomes large. On the other hand, in the case of embodiment 1, as shown in fig. 12, the screw rotation speed is controlled in accordance with the developer humidity, and therefore, it can be understood that improper discharge on the high humidity side is mitigated, and robustness against developer overflow is ensured. Here, it is understood that the developer charge amount is affected not only by the developer humidity but also by the image duty. Therefore, in both comparative example and example 1, when the image duty becomes high, the replacement of the toner in the developing container becomes large, and therefore, the charge amount decreases, and the developer amount increases.

Further, in the case of the present embodiment, in the case where the developer humidity is low, the charging amount is high, and the fluidity is low, the screw rotation speed is set to a low value. For this reason, by suppressing a high load applied to the developer having low fluidity, it is possible to prevent screw locking and developer deterioration due to an increase in screw load.

< second embodiment >

A second embodiment of the present invention will be described using fig. 13 to 15. In the first embodiment described above, by controlling the screw rotation speed in accordance with the developer humidity, the discharge characteristic of the developer at a low charge amount under a high humidity environment is promoted, thereby improving the robustness against developer overflow. However, the developer charge amount depends not only on the environment to a large extent but also on the image duty. Therefore, in the present embodiment, the developer discharge is improved by controlling the screw rotation speed according to the image duty. Other configurations and actions are similar to those in the first embodiment described above, and therefore redundant illustration and description will be omitted or briefly made, and the same reference numerals are added to the same constituent elements, and hereinafter, different portions from the first embodiment will be mainly described.

First, the reason why the developer charge amount changes according to the image duty is that the stirring time in the developing container 22 with respect to the amount of supplied toner differs, and therefore, the stirring time distribution of the toner in the developing container 22 differs. That is, in the case of continuously printing images with a high image duty, most of the toner in the developing container 22 is used for developing the latent image, and therefore, new (fresh) toner is supplied. At this time, when DUTY is higher, a large amount of toner is supplied in a short time. Therefore, the stirring time distribution of the toner in the developing container 22 is mainly occupied by a short time, so that the overall charge amount is reduced due to insufficient stirring. On the other hand, in the case where a low DUTY image is continuously printed, the toner is rarely replaced, so that the stirring time distribution of the toner in the developing container 22 is mainly occupied by a long time. Therefore, the charge amount increases as a whole.

Therefore, in the present embodiment, as the information on the developer charge amount, the image duty is used. For this purpose, as shown in fig. 13, the image forming apparatus in the present embodiment includes a CPU 50 as a control means, a memory 51 as a storage means, a counter 52 for counting the number of image-formed sheets (the number of sheets subjected to image formation), and a video counting section 57. In the present embodiment, the counter 52 and the video counting portion 57 constitute a toner consumption amount detecting portion 58 as an acquiring portion and a toner consumption amount detecting means.

The video count portion 57 integrates the number of image dots (i.e., video count) formed on the photosensitive drum. For example, the video counting section 57 integrates the gradation (0 to 255 gradations) per (one) pixel of the input image data (for example, at 600dpi) for each image (sheet) surface. Further, the number of image forming sheets is counted by the counter 52, the video count corresponding to the specific number of image forming sheets is integrated, and divided by a value obtained by multiplying the number of image forming sheets by the video count having 100% DUTY, thereby obtaining an average image DUTY. That is, the average image duty is an average image duty of the specific number of image forming sheets, and corresponds to a value related to the amount of consumption of toner consumed per unit time of image formation. Therefore, when the average image duty ratio is high, a case is shown in which the amount of consumption of toner consumed per unit time is large, and, in this case, a large amount of new (fresh) developer is supplied into the developing container 22, so that there is a tendency that the developer charge amount is reduced. On the other hand, when the average image duty is low, a case is shown where the amount of consumption of the toner consumed per unit time is small, and in this case, the replacement of the developer in the developing container 22 is small, so that there is a tendency that the developer charge amount increases. In the present embodiment, the average image duty is calculated by the toner consumption amount detecting portion 58.

In the present embodiment, information obtained by calculating the average image duty (toner consumption amount) by the toner consumption amount detecting portion 58 is stored in the memory 51. Further, also in the case of the present embodiment, during the rising of the developing device 4 (the time of switching from OFF to ON), the CPU 50 reads the average image duty at this time from the memory 51, and determines the driving speed of the first feed screw 25 (screw rotation speed) from the table of table 2 based ON the information thereof. In the present embodiment, as shown in table 2, three tables are provided, and each table can be selected by the user or the like in the service mode. The initial settings are table 2.

Table 2 all units are rpm

In each table of Table 2, the screw rotation speed (unit: "rpm") is set for the average image duty. Incidentally, table 1 is a pattern in which the screw rotation speed is constant regardless of the average image duty. On the other hand, in tables 2 and 3, the screw rotation speed is set so as to be faster in the case where the average image duty (toner consumption amount) corresponds to the second consumption amount that is larger than the first consumption amount than in the case where the average image duty (toner consumption amount) is the first consumption amount. For example, when the average image duty as a value related to the first consumption amount is 20% or less, the screw rotation speed is 700rpm, and when the average image duty as a value related to the second consumption amount is greater than 20%, the screw rotation speed is 800rpm or more.

Incidentally, in the present embodiment, the calculation of the average image duty for the screw rotation speed is performed at the time of image formation of a predetermined number of sheets. For this reason, the number of image forming sheets is counted by the counter 52, and when the value counted by the counter 52 is not less than the predetermined number of sheets during the rising of the developing device 4, the average image duty is calculated and stored in the memory 51. Then, the CPU 50 controls the screw rotation speed based on the average image duty. Therefore, in the case of the present embodiment, the average image duty is an average value of the image duty values from the update (control) of the screw rotation speed to the subsequent update of the screw rotation speed.

Using fig. 14, a specific example of control in the present embodiment will be described. Further, in the present embodiment, the flowchart of fig. 14 is executed every time the developing device 4 is raised (OFF/ON), and the driving is started at the screw rotation speed acquired therefrom. That is, in the present embodiment, the timing of change in the screw rotation speed is the timing of development drive OFF/ON.

First, every time the development drive is OFF/ON, the number of image forming sheets (print number) c (n) at this time is read from the memory 51, and the image forming sheets number c (n) is compared with the print number Cd in which the last screw rotation speed is changed with the average image duty (S11). When c (n) -Ch is not less than 1000 sheets (yes at S11), the integral image point number B at this time obtained separately by the calculation is read from the memory 51. Then, by dividing the number of image dots B by B _ max (c (n) -Cd), the screw rotation speed is updated in accordance with the average image duty of the previous time, and then the average image duty < D > of printing one sheet at a time until this time is acquired (S12). Here, b _ max is the number of image dots when the average image duty is 100% image duty when printing one a4 size. Further, the integral image point number B is a number added in real time by calculating B ═ B + B (n) each time one sheet is printed, where the image point number at this time is B (n).

The average image duty < D > acquired in S12 is stored in the memory 51 (S13), and the number of points B of integration is cleared for the subsequent calculation of the average image duty (S14). C (n) at this time is set to the closest sheet number Cd in which the screw rotation speed is changed according to the average image duty (S15), and the development drive is actuated using the average image duty < D > stored in the memory 51 (S16). That is, the screw rotation speed at the average image duty < D > is read from the table of table 2, and the drive of the developing device is actuated at the screw rotation speed. On the other hand, in S11, when the difference from the print number Cd in which the screw rotation speed of the last time changed with the average image duty is less than 1000 sheets (no of S11), the development drive is actuated using the average image duty < D > of the last time (S16). That is, < D > is not updated, and therefore, the development drive is actuated at the screw rotation speed of the previous time as it is. By performing the above sequence, the screw rotation speed is updated at a certain frequency (1000 sheets or more in the present embodiment), so that the screw rotation speed corresponding to the average image duty at that time can be set.

In the case of the present embodiment as described above, in a state where the charge amount is low where the developer fluidity is high, that is, in a state where the average image duty is high (the toner consumption amount is large), control is performed so that the driving speed of the first feed screw 25 is fast. For this reason, similarly to the first embodiment, even when the developer fluidity is high and the developer is not easily stagnated in the vicinity of the discharge port 40, the developer surface is raised, so that the discharge of the developer can be appropriately performed.

The effects of the present embodiment as described above will be described using fig. 11 and 15. Fig. 11 and 15 show the results of experiments performed to confirm the effects of the present example. Experiments were conducted under the following conditions for each of the comparative example in which the screw rotation speed was made constant regardless of the average image duty ratio and example 2 in which the screw rotation speed was varied with the average image duty ratio as in the present example. First, the image duty (image duty) is changed to a plurality of levels, the developing device is driven in each of the environments in which the developer humidity is different, and the developer amounts in the developing containers are compared. Fig. 11, 15 show developer amounts, fig. 11 shows results of comparative example, and fig. 15 shows results of example 2. In the comparative example, the screw rotation speed was constantly 700 (rpm). In example 2, the screw rotation speed was controlled using table 2 of table 2.

According to fig. 11, in the case of the comparative example in which the screw rotation speed is not controlled and made constant according to the average image duty, the developer amount fluctuates according to the average image duty. In particular, in the case where the average image duty is 10%, the developer discharge amount is significantly reduced and compensated with the developer amount in the developing container, and thus the developer amount is increased as compared to when the average image duty is 0%. Further, the tendency also depends on the developer humidity as described in the first embodiment, and is remarkable particularly in a high humidity environment. In summary, as described above, in the comparative example, for developer overflow having a higher image duty and a higher humidity, the robustness becomes lower, so that the risk of developer overflow due to developer surface fluctuation of the moment during driving OFF/ON or the like becomes large.

On the other hand, in the case of embodiment 2, as shown in fig. 15, the screw rotation speed is controlled according to the average image duty, so that the variation in the discharge amount due to the image duty is suppressed, and the variation in the developer amount of 0% to 100% in the entire humidity environment is small. Therefore, it can be understood that the robustness against developer overflow is improved as compared with the comparative example.

< third embodiment >

A third embodiment of the present invention will be described using fig. 16 to 18. In the first and second embodiments described above, by controlling the screw rotation speed according to the developer humidity or the average image duty, the discharge characteristic of the developer at a low charge amount is promoted, thereby improving the robustness against developer overflow. In the present embodiment, the developer discharge is further improved by controlling the screw rotation speed in accordance with these two parameters consisting of the developer humidity and the image duty. Other configurations and actions are similar to those in the first and second embodiments described above, and therefore redundant illustration and description will be omitted or briefly made, and the same reference numerals are added to the same constituent elements, and hereinafter, different portions from the first and second embodiments will be mainly described.

Therefore, also in the present embodiment, as the information on the developer charge amount, the developer humidity and the image duty are used. For this purpose, as shown in fig. 16, the image forming apparatus in the present embodiment includes a CPU 50 as a control means, a memory 51 as a storage means, a counter 52 for counting the number of image-formed sheets (the number of sheets subjected to image formation), a humidity detection section 53 as an acquisition section and humidity detection means, and a video counting section 57. Further, in the present embodiment, the counter 52 and the video counting portion 57 constitute a toner consumption amount detecting portion 58 as an acquiring portion and a toner consumption amount detecting means. Further, also in the case of the present embodiment, the humidity detection portion 53 includes a water content sensor 54 as a water content detection means, a temperature sensor 55 as a temperature detection means, and a calculation portion 56 as a calculation means. The structures and actions of the respective portions are similar to those in the first embodiment and the second embodiment.

In the case of the present embodiment, when image formation is performed on the first number of sheets or more of recording material from the time when the humidity (humidity information) detected by the humidity detecting portion 53 was last stored in the memory 51, the CPU 50 stores the humidity information (humidity information) detected by the humidity detecting portion 53 in the memory 51. That is, the humidity information in the memory 51 is updated. Further, when image formation is performed on the recording material of the second number of sheets or more since the average image duty detected by the toner consumption amount detecting portion 58 was last stored in the memory 51, the CPU 50 stores the average image duty detected by the toner consumption amount detecting portion 58 in the memory 51. Here, the second number of sheets is different from and more than the first number of sheets. For example, the first sheet number is 300 sheets, and the second sheet number is 1000 sheets.

Then, the CPU 50 controls the second drive motor M2 based on a speed set from the relationship between the humidity (humidity information) and the average image duty (toner consumption amount) stored in the memory 51. In the present embodiment, the CPU 50 determines the driving speed (screw rotation speed) of the first feed screw 25 from the table of table 3. Further, in the present embodiment, as shown in table 3, three tables are provided, and each table can be selected by the user or the like in the service mode. The initial settings are table 2. Here, the reason why a plurality of tables are provided in the service mode as in table 3 is that a more appropriate table can be selected according to a specific user or area (environment).

Table 3 all units are rpm

In each table of Table 3, the screw rotation speed (unit: "rpm") was set for the developer humidity and the average image duty. Incidentally, table 1 is a mode in which the screw rotation speed is constant regardless of the developer humidity and the average image duty. On the other hand, in tables 2 and 3, the screw rotation speed is set so that the rotation speed is faster in the case where the developer humidity is the second humidity (for example, more than 15%) higher than the first humidity than in the case where the developer humidity is the first humidity (for example, 15% or less). Also, setting is made such that the screw rotation speed is faster in the case where the average image duty (toner consumption amount) corresponds to a second consumption amount that is larger than the first consumption amount (for example, larger than 20%) than in the case where the average image duty (toner consumption amount) corresponds to the first consumption amount (for example, not larger than 20%).

Using fig. 17, a specific example of control in the present embodiment will be described. Further, in the present embodiment, the flowchart of fig. 17 is executed every time the developing device 4 is raised (OFF/ON), and the driving is started at the screw rotation speed acquired therefrom. That is, also in the present embodiment, the timing of change in the screw rotation speed is the timing of development drive OFF/ON.

First, every time the development drive is OFF/ON, the number of image forming sheets (print number) c (n) at this time is read from the memory 51, and the image forming sheets number c (n) is compared with the print number Ch in which the last developer humidity H in the memory 51 is updated (S21). Then, when c (n) -Ch is not less than 300 sheets (yes at S21), the developer humidity at this time is read from the memory 51 and set as the developer humidity H for screw rotation speed control (S22). The developer humidity is calculated every printing and stored in the memory 51. Thereafter, the print number c (n) at this time is used as the sheet number Ch of the latest updated developer humidity H (S23), and the sequence proceeds to the subsequent S24. On the other hand, in S21, when c (n) -Ch is less than 300 sheets (no of S21), the developer humidity H is not updated, and the last developer humidity H is maintained as it is, so that the sequence proceeds to the subsequent S24.

Next, the print number c (n) read from the memory 51 is compared with the print number Cd of the average image duty in the update memory 51 (S24). When c (n) -Cd is not less than 1000 sheets (yes at S24), the integral image point number B at this time obtained separately by calculation is read from the memory 51. Then, the average image duty at the previous time is updated by dividing the number of image dots B by B _ max (c (n) — Cd), and then the average image duty < D > for each printing one sheet until this time is acquired (S25).

The average image duty < D > acquired in S25 is stored in the memory 51 (S26), and the number of points B of integration is cleared for the subsequent calculation of the average image duty (S27). C (n) at this time is set as the closest sheet number Cd in which the average image duty is updated (S28), and the development drive is actuated using the developer humidity and the average image duty < D > stored in the memory 51 (S29). That is, the screw rotation speed at the developer humidity and the average image duty < D > is read from the table of table 3, and the drive of the developing device is actuated at the screw rotation speed.

On the other hand, in S25, when c (n) -Cd is less than 1000 sheets (no of S24), the average image duty ratio < D > is not updated and the last average image duty ratio < D > is maintained as it is, and the sequence proceeds to S29. By performing the above sequence, the screw rotation speed is updated at a certain frequency (300 sheets or more, or 1000 sheets or more in the present embodiment), so that the screw rotation speed corresponding to the developer humidity and the average image duty at that time can be set. In the case of the present embodiment as described above, the rotation speed of the screw is controlled using the developer humidity and the average image duty, and therefore the developer discharge can be performed with high accuracy.

The effects of the present embodiment as described above will be described using fig. 11 and 18. Fig. 11 and 18 show the results of experiments performed to confirm the effects of the present example. For each of the comparative example in which the screw rotation speed was made constant regardless of the developer humidity and the average image duty and the example 3 in which the screw rotation speed was varied with the developer humidity and the average image duty as in the present example, an experiment was performed under the following conditions. First, the image duty (image duty) is changed to a plurality of levels, the developing device is driven in each of the environments in which the developer humidity is different, and the developer amounts in the developing containers are compared. Fig. 11, 18 show developer amounts, fig. 11 shows results of comparative example, and fig. 18 shows results of example 3. In the comparative example, the screw rotation speed was constantly 700 (rpm). In example 3, the screw rotation speed was controlled using table 2 of table 3.

As shown in fig. 18, in embodiment 3, the screw rotation speed is controlled in accordance with two parameters consisting of the developer humidity and the average image duty, and therefore, even compared with the cases of embodiment 1 and embodiment 2, the variation in the discharge amount can be more effectively suppressed. As a result thereof, it can be understood that the robustness against developer overflow is improved.

< fourth embodiment >

A fourth embodiment of the present invention will be described using fig. 18 to 20. In the third embodiment described above, by controlling the screw rotation speed in accordance with both the developer humidity and the average image duty, the discharge characteristic of the developer at a low charge amount is promoted, thereby improving the robustness against developer overflow. However, when the ambient temperature and the ambient humidity of the developer change sharply, the developer humidity cannot immediately follow the change, and gradually adapts to the ambient environment of the developer while being delayed to some extent. For this reason, for some time from the occurrence of variations in the ambient temperature and humidity of the developer, a case where inconsistency occurs between the original developer state (charge amount) and the developer state (charge amount) detected and determined as described above will be considered. Therefore, in the present embodiment, even in the case where the inconsistency is generated as described above, the change of the screw rotation speed is not immediately performed within a certain period of time, so that the influence thereof is small. Other configurations and actions are similar to those in the third embodiment described above, and therefore redundant illustration and description will be omitted or briefly made, and the same reference numerals are added to the same constituent elements, and hereinafter, different portions from the third embodiment will be mainly described.

Therefore, also in the present embodiment, similarly to the third embodiment, as the information on the developer charging amount, the developer humidity and the image duty are used. For this purpose, as shown in fig. 16, the image forming apparatus in the present embodiment also includes a CPU 50, a memory 51, a counter 52, and a video counting section 57. Further, in the present embodiment, the counter 52 and the video counting portion 57 constitute a toner consumption amount detecting portion 58 as an acquiring portion and a toner consumption amount detecting means. The structures and actions of the respective portions are similar to those in the first embodiment and the second embodiment.

Further, in the case of the present embodiment, the CPU 50 controls the screw rotation speed based on the developer humidity and the average image duty ratio stored in the memory 51. However, in the case where the humidity detected by the humidity detecting portion 53 at a predetermined timing (in the present embodiment, during the development driver OFF/ON period) greatly changes with respect to the humidity stored in the memory 51, the information ON the humidity of the developer is not updated for a while. That is, a case where the currently detected humidity (humidity information) changes from a low humidity section, which is (corresponds to) a predetermined humidity range, to a high humidity section, which is (corresponds to) a humidity range in which the humidity is higher than the low humidity section, with respect to the previously detected humidity (humidity information) will be considered. In this case, the humidity stored in the memory 51 is not updated from the time of change until an image is formed on a predetermined number of sheets of recording material. That is, the humidity maintained at the last value is used to control the screw rotation speed. On the other hand, in the case other than that, similarly to the third embodiment, the humidity stored in the memory 51 is updated with the humidity detected at this time, and the screw rotation speed is controlled using the (updated) humidity.

In other words, when the ambient environment of the developer changes the developer humidity from the low humidity section to the high humidity section, the screw rotation speed is not changed immediately, but remains as it is until a predetermined number of sheets (500 sheets in the present embodiment) are printed. Thereafter, after the number of sheets exceeds 500, the screw rotation speed is first changed during the development driver OFF/ON mode according to the detected humidity.

Incidentally, the humidity section in the present embodiment includes the section shown in the above table 3, in which the humidity section is divided into three sections. That is, the first section is "15% or less", the second section is "more than 15% and 45% or less", and the third section is "more than 45%". Therefore, a case where the currently detected humidity changes from a low humidity section, which is a predetermined humidity range, to a high humidity section, which is a humidity range in which the humidity is higher than that of the low humidity section, with respect to the previously detected humidity is the following case. That is, this case is a case where the previously detected humidity is within the range of the first section and the currently detected humidity is within the range of the second section or the third section, or a case where the previously detected humidity is within the range of the second section and the currently detected humidity is within the range of the third section. In this case, the screw rotation speed is not changed immediately, and the screw rotation speed is kept as it is until printing of a predetermined number of sheets is performed.

Here, in the screw rotation speed control, in the case where the developer humidity determined by detection using the temperature sensor or the water content sensor and the actual developer humidity do not match each other, the most harmful effect is liable to be produced as follows. That is, the case is such that: although the developer has not so high humidity, the detected and determined humidity is high humidity, the screw is driven at a faster rotation speed than the original screw rotation speed, and the developer is excessively discharged. This is because the speed at which the developer is reduced due to excessive developer discharge is generally fast, and the developer is quickly exhausted and cannot be sufficiently supplied to the developing sleeve, so that the possibility of generating image defects (e.g., density unevenness) increases.

On the other hand, the case of improper developer discharge that is not continuous for a long period of time becomes serious, but in the period in which the above-described humidity is not matched temporarily, the risk of causing overflow or the like due to the increase of the developer is small. Further, in the case where the ambient environment of the developer changes from low humidity to high humidity, the developer follows the environment with a certain degree of delay, and therefore, it will be considered that the above-described problem is relatively likely to occur less. For the reason described above, in the present embodiment, the screw rotation speed control according to the developer humidity is not performed until 500 sheets of printing are performed from the time when the developer humidity detected by the temperature sensor or the water content sensor is switched from the low humidity section to the high humidity section.

On the other hand, the humidity section is switched from high humidity to low humidity based on the detection of the temperature sensor or the water content sensor as follows. That is, the case is such that: even if the detected developer humidity and the actual developer humidity do not match each other, the detected and determined humidity is a low humidity although the humidity of the developer is not too low. This case is a case where the screw is driven at a slower rotational speed than the original screw rotational speed and improper developer discharge occurs. As described above, the case where such a state lasts for a long time becomes serious, but the detected developer humidity and the actual developer humidity gradually coincide with each other as the screw is driven, and therefore, when the above developer humidity temporarily does not match, the risk of overflow or the like due to the increase of the developer is small. Therefore, in this case, it is not necessary to perform control so that the change of the screw rotation speed is not performed during the switching from the low humidity to the high humidity.

Using fig. 19 and 20, a specific example of control in the present embodiment will be described. Further, in the present embodiment, the flowchart of fig. 19 is executed every time the developing device 4 is raised (OFF/ON), and the driving is started at the screw rotation speed acquired therefrom. That is, also in the present embodiment, the timing of change in the screw rotation speed is the timing of development drive OFF/ON. Incidentally, the flow of fig. 19 is the same as the flow of fig. 17 described above in many parts, and therefore, the same steps are omitted from or briefly described from the description, and, with regard to fig. 19, parts different from the flow of fig. 17 will be mainly described.

First, it is checked at each development drive OFF/ON whether a flag described later is K0 (S31). When K is 0 (yes at S31), that is, when the flag is not set, the number of image forming sheets (print number) c (n) at this time is compared with the print number Ch in which the last screw rotation speed was changed according to humidity (S32). Then, it is judged whether or not the developer humidity H (n) expected to be currently updated changes from the low humidity section to the high humidity section in the table of table 3 with respect to the previously updated developer humidity H (i.e., the developer humidity H stored in the memory 51) (S33). If the developer humidity H is not switched from the low humidity section to the high humidity section (no at S33), K remains 0 as it is (S34), and the sequence proceeds to S35. That is, the developer humidity at this time is read from the memory 51, and set as the developer humidity H for screw rotation speed control (S35). Thereafter, the print number c (n) at this time is used as the sheet number Ch of the latest updated developer humidity H (S36), and the sequence proceeds to the subsequent S38.

In S33, the developer humidity is switched from the low humidity section (yes in S33), the screw rotation speed holding flag K is set to 1(K ═ 1), the developer humidity H is not updated and is kept as it is, and the sequence goes to control with the average image duty (S37). S38 to S43 are the same as S24 to S29 in fig. 17, and thus description will be omitted. Thereafter, every time the development drive is OFF/ON, in the first flow, it is checked whether K is 1(S31), when K is 1, the sequence unconditionally enters control using the average image duty, and S38 and subsequent steps are performed.

Here, switching of K from 0 to 1 (erasing (resetting) of the flag) is performed from the time the print count reaches the number of print sheets of which K is 1 until the print count is counted as 500 sheets. This flow is shown in fig. 20. That is, at the start of printing (not at the start of a print job), it is checked whether K is 1 (S51). Then, when K is 1 (yes at S51), the print number L is counted (S52), and when L is 500 sheets or more (yes at S53), K is 0 and L is 0(S54) are set. Thus, from the time when K becomes 1, 500 or more prints are made, and the flag is eliminated (reset), so that the sequence can proceed to S32 and subsequent steps in fig. 19.

For example, in table 3 of table 3, a case where the interval of the screw rotation speed is changed from the interval (900rpm) of "humidity is 15% to 45% and average image duty is 20% to 50%" to a higher humidity interval (for example, humidity: 60%) will be described. In this case, K is 1, and the developer humidity H is not updated, but if the image DUTY simultaneously becomes high DUTY and exceeds 50%, the section of the screw rotation speed is a section of "humidity is 15% to 45%, and the average image DUTY is 50% or more". Then, the screw rotation speed was changed from 900rpm to 1100 rpm. After that, 500 sheets of printing were performed, and when K is 0, the humidity was 60%, and therefore, the interval of the screw rotation speed was "humidity was 45% or more and average image duty was 50% or more" so that the screw rotation speed was changed from 1100rpm to 1400 rpm.

In the case of the present embodiment, by performing the control as described above, while reducing the risk of humidity in different environments not matching as described above, it is possible to select an optimum screw rotation speed according to the environment and the image duty of the printed image. As a result thereof, image defects such as developer overflow are suppressed, so that stable images can be obtained over a long period of time.

< other examples >

In the above-described embodiment, the number of image forming sheets is counted for updating the developer humidity H and the average image duty < D > and for erasing (resetting) the flag K, but this may be replaced with the driving time of the developing sleeve. Further, the drive source of the developing sleeve and the feed screw are separately provided, but the same drive source may be used.

Further, in the above-described embodiment, the vertical agitation type developing device is used in which the developing chamber 23 having the function of supplying the developer to the developing sleeve 23 and the agitating chamber 24 having the function of recovering the developer from the developing sleeve 28 are vertically arranged, respectively. However, the present invention is also applicable to an image forming apparatus including a developing device having a configuration other than this configuration. For example, as shown in fig. 21, when the drive source of the developing sleeve 28 and the drive sources of the feed screws 25, 26 are provided separately from each other, a horizontal stirring type developing device in which the developing chamber 23 and the stirring chamber 24 are horizontally arranged may also be used. Further, as shown in fig. 22, even in the vertical agitation type, when the driving sources of the developing sleeve 28 and the feeding screws 25, 26 are provided separately from each other, it is possible to use a developing apparatus in which the function of supplying the developer to the developing sleeve 28 and the function of recovering the developer after being used for developing the latent image are not separated from each other.

[ Industrial Applicability ]

According to the present invention, even when the fluidity of the developer is high and the developer is not easily stagnated in the vicinity of the discharge port, there is provided an image forming apparatus capable of appropriately discharging the developer by raising the developer surface.

[ description of reference numerals ]

1(1a, 1b, 1c, 1d). photosensitive drum (image bearing member)/4 (4a, 4b, 4c, 4d). developing device (developing means)/22.. developing container/25.. first feed screw/25 a.. rotation shaft/25 b.. blade/26.. second feed screw/31.. hopper (feed means)/32.. feed screw/40.. discharge port/50.. CPU (controller)/51.. memory (storage means)/52.. counter/53.. humidity detection portion (acquisition portion, humidity detection portion)/54.. water content sensor (water content detection means 55.. temperature sensor (temperature detection means)/56.. calculation portion (calculation means)/57.. video counting portion/58.. toner consumption detection portion)/56.. toner consumption detection portion (calculation means)/first toner drive means drive region/100.. second toner drive motor drive means/21.

Claims

1. An image forming apparatus capable of performing image formation on a plurality of recording materials, comprising:

an image bearing member;

a developing device configured to develop an electrostatic latent image formed on the image bearing member with a developer containing toner and carrier, the developing device including,

a developing container capable of containing the developer and including a first chamber and a second chamber partitioned from the first chamber by a partition wall,

a first flow-through portion configured to allow a flow-through of developer from the first chamber to the second chamber,

a second flow-through portion configured to allow a flow-through of developer from the second chamber to the first chamber,

a first feed screw disposed in the first chamber and configured to feed the developer in a first direction from the second flow portion toward the first flow portion,

a second feed screw disposed in the second chamber and configured to feed the developer in a second direction from the first flow portion toward the second flow portion, and

a discharge portion, provided in a side wall of the first chamber, upstream of the first flow-through portion and downstream of the second flow-through portion with respect to a first direction, and configured to allow a portion of the developer to be discharged from the developing device,

a supply device configured to supply the developer to the developing container,

a drive device configured to rotatably drive the first feed screw;

a first acquisition portion configured to acquire information on relative humidity in the developing container, an

A second acquisition section configured to acquire information on an amount of toner consumed by image formation on the plurality of recording materials, an

A controller configured to control the driving device,

wherein the first feed screw is provided with a vane portion in a first region of the first feed screw positioned upstream of the discharge portion and downstream of the second flow-through portion with respect to the first direction, and the first feed screw is not provided with a vane portion in a second region of the first feed screw that is opposite to the discharge portion, and wherein the first feed screw is provided with no vane portion in a second region of the first feed screw that is opposite to the discharge portion

Wherein the controller controls a driving speed of the driving device for rotatably driving the first feeding screw based on the information on the relative humidity in the developing container acquired by the first acquiring portion and the information on the amount of toner consumed by image formation on the plurality of recording materials acquired by the second acquiring portion.

2. An image forming apparatus according to claim 1, wherein the controller controls a driving speed of the driving device for rotatably driving the first feed screw such that the driving speed is a first driving speed in a case where an amount of toner consumed by image formation on the plurality of recording materials is a predetermined consumption amount and the relative humidity in the developing container is a first value, and the driving speed is a second driving speed faster than the first driving speed in a case where the amount of toner consumed by image formation on the plurality of recording materials is the predetermined consumption amount and the relative humidity in the developing container is a second value higher than the first value.

3. An image forming apparatus according to claim 1, wherein the controller controls a driving speed of the driving device for rotatably driving the first feed screw such that the driving speed is a third driving speed in a case where the relative humidity in the developing container is a predetermined value and the amount of toner consumed by image formation on the plurality of recording materials is a first consumption amount, and the driving speed is a fourth driving speed faster than the third driving speed in a case where the relative humidity in the developing container is a predetermined value and the amount of toner consumed by image formation on the plurality of recording materials is a second consumption amount higher than the first consumption amount.

4. An image forming apparatus according to claim 1, wherein the controller controls a driving speed of the driving device for rotatably driving the first feed screw such that the driving speed is a fifth driving speed in a case where the relative humidity in the developing container is a first value and the amount of toner consumed by image formation on the plurality of recording materials is a first consumption amount, and the driving speed is a sixth driving speed faster than the fifth driving speed in a case where the relative humidity in the developing container is the first value and the amount of toner consumed by image formation on the plurality of recording materials is a second consumption amount higher than the first consumption amount, and

controlling a driving speed of the driving device for rotatably driving the first feeding screw such that the driving speed is a sixth driving speed in a case where the relative humidity in the developing container is a first value and the amount of toner consumed by image formation on the plurality of recording materials is a second consumption amount, and the driving speed is a seventh driving speed faster than the sixth driving speed in a case where the relative humidity in the developing container is a second value higher than the first value and the amount of toner consumed by image formation on the plurality of recording materials is the second consumption amount.

5. An image forming apparatus according to claim 4, wherein the controller controls a driving speed of the driving device for rotatably driving the first feed screw such that the amount of toner consumed by image formation on the plurality of recording materials is a first consumption amount and the driving speed is a fifth driving speed in a case where the relative humidity in the developing container is a first value, and the driving speed is an eighth driving speed faster than the fifth driving speed in a case where the amount of toner consumed by image formation on the plurality of recording materials is the first consumption amount and the relative humidity in the developing container is a second value higher than the first value, and

controlling a driving speed of the driving device for rotatably driving the first feeding screw such that the driving speed is an eighth driving speed in a case where an amount of toner consumed by image formation on the plurality of recording materials is a first consumption amount and the relative humidity in the developing container is a second value, and the driving speed is a seventh driving speed faster than the eighth driving speed in a case where the amount of toner consumed by image formation on the plurality of recording materials is a second consumption amount higher than the first consumption amount and the relative humidity in the developing container is the second value.

6. An image forming apparatus according to claim 1, wherein the controller controls a driving speed of the driving device for rotatably driving the first feed screw such that the driving speed is a fifth driving speed in a case where an amount of toner consumed by image formation on the plurality of recording materials is a first consumption amount and the relative humidity in the developing container is a first value, and the driving speed is a sixth driving speed faster than the fifth driving speed in a case where the amount of toner consumed by image formation on the plurality of recording materials is the first consumption amount and the relative humidity in the developing container is a second value higher than the first value, and

controlling a driving speed of the driving device for rotatably driving the first feeding screw such that the driving speed is a sixth driving speed in a case where an amount of toner consumed by image formation on the plurality of recording materials is a first consumption amount and the relative humidity in the developing container is a second value, and the driving speed is a seventh driving speed faster than the sixth driving speed in a case where the amount of toner consumed by image formation on the plurality of recording materials is a second consumption amount higher than the first consumption amount and the relative humidity in the developing container is the second value.

7. An image forming apparatus according to any one of claims 1 to 6, wherein the controller controls a driving speed of the driving device for rotatably driving the first feed screw in a case where the rotational driving of the first feed screw is started in a state where the rotational driving of the first feed screw is stopped.

8. The image forming apparatus according to any one of claims 1 to 6, wherein the information on the amount of toner consumed by image formation on the plurality of recording materials is an average image duty in image formation on the plurality of recording materials performed over a period from control of a driving speed of the driving device for rotatably driving the first feeding screw by the controller to subsequent control of the driving speed of the driving device for rotatably driving the first feeding screw by the controller.

9. The image forming apparatus according to claim 1, wherein the first acquisition portion acquires information relating to relative humidity in the developing container and information relating to temperature in the developing container, and

wherein the controller controls a driving speed of the driving device for rotatably driving the first feeding screw, based on the information on the relative humidity in the developing container acquired by the first acquiring portion, the information on the temperature in the developing container acquired by the first acquiring portion, and the information on the amount of toner consumed by image formation on the plurality of recording materials acquired by the second acquiring portion.

10. An image forming apparatus according to any one of claims 1 to 6, wherein the first feed screw is provided with a blade portion in a third region of the first feed screw positioned downstream of the discharge portion and upstream of the first flow-through portion with respect to the first direction.

11. An image forming apparatus according to claim 1, wherein said developing device further comprises a developer carrying member configured to feed said developer to a developing area opposite to said image carrying member while carrying said developer, and

wherein, in the first chamber, the developer is supplied to the developer carrying member.

12. An image forming apparatus capable of performing image formation on a plurality of recording materials, comprising:

an image bearing member;

a supply device configured to supply the developer to the developing container,

a drive device configured to rotatably drive the first feed screw;

A controller configured to control the driving device,

wherein the first feed screw is provided with a vane portion having a first outer diameter in a first region of the first feed screw positioned upstream of the discharge portion and downstream of the second flow-through portion with respect to the first direction, and is provided with a vane portion having a second outer diameter in a second region of the first feed screw opposite to the discharge portion, the second outer diameter being smaller than the first outer diameter, and

13. An image forming apparatus according to claim 12, wherein the controller controls a driving speed of the driving device for rotatably driving the first feed screw such that the driving speed is a first driving speed in a case where an amount of toner consumed by image formation on the plurality of recording materials is a predetermined consumption amount and the relative humidity in the developing container is a first value, and the driving speed is a second driving speed faster than the first driving speed in a case where the amount of toner consumed by image formation on the plurality of recording materials is the predetermined consumption amount and the relative humidity in the developing container is a second value higher than the first value.

14. An image forming apparatus according to claim 12, wherein the controller controls a driving speed of the driving device for rotatably driving the first feed screw such that the driving speed is a third driving speed in a case where the relative humidity in the developing container is a predetermined value and the amount of toner consumed by image formation on the plurality of recording materials is a first consumption amount, and the driving speed is a fourth driving speed faster than the third driving speed in a case where the relative humidity in the developing container is a predetermined value and the amount of toner consumed by image formation on the plurality of recording materials is a second consumption amount higher than the first consumption amount.

15. An image forming apparatus according to claim 12, wherein the controller controls a driving speed of the driving device for rotatably driving the first feed screw such that the driving speed is a fifth driving speed in a case where the relative humidity in the developing container is a first value and the amount of toner consumed by image formation on the plurality of recording materials is a first consumption amount, and the driving speed is a sixth driving speed faster than the fifth driving speed in a case where the relative humidity in the developing container is the first value and the amount of toner consumed by image formation on the plurality of recording materials is a second consumption amount higher than the first consumption amount, and

16. An image forming apparatus according to claim 15, wherein the controller controls a driving speed of the driving device for rotatably driving the first feed screw such that the amount of toner consumed by image formation on the plurality of recording materials is a first consumption amount and the driving speed is a fifth driving speed in a case where the relative humidity in the developing container is a first value, and the driving speed is an eighth driving speed faster than the fifth driving speed in a case where the amount of toner consumed by image formation on the plurality of recording materials is the first consumption amount and the relative humidity in the developing container is a second value higher than the first value, and

17. An image forming apparatus according to claim 12, wherein the controller controls a driving speed of the driving device for rotatably driving the first feed screw such that the driving speed is a fifth driving speed in a case where an amount of toner consumed by image formation on the plurality of recording materials is a first consumption amount and the relative humidity in the developing container is a first value, and the driving speed is a sixth driving speed faster than the fifth driving speed in a case where the amount of toner consumed by image formation on the plurality of recording materials is the first consumption amount and the relative humidity in the developing container is a second value higher than the first value, and

18. An image forming apparatus according to any one of claims 12 to 17, wherein the controller controls a driving speed of the driving device for rotatably driving the first feed screw in a case where the rotational driving of the first feed screw is started in a state where the rotational driving of the first feed screw is stopped.

19. An image forming apparatus according to any one of claims 12 to 17, wherein the information on the amount of toner consumed by image formation on the plurality of recording materials is an average image duty in image formation on the plurality of recording materials performed over a period from control of a driving speed of the driving device for rotatably driving the first feeding screw by the controller to subsequent control of the driving speed of the driving device for rotatably driving the first feeding screw by the controller.

20. An image forming apparatus according to claim 12, wherein said first acquisition portion acquires information relating to relative humidity in said developing container and information relating to temperature in said developing container, and

21. An image forming apparatus according to any one of claims 12 to 17, wherein the first feed screw is provided with a blade portion in a third region of the first feed screw positioned downstream of the discharge portion and upstream of the first flow-through portion with respect to the first direction.

22. An image forming apparatus according to claim 12, wherein said developing device further comprises a developer carrying member configured to feed said developer to a developing area opposite to said image carrying member while carrying said developer, and